In the case of laser cutting machines for metal machining, in particular for cutting workpieces of flat material, the laser cutting head can be displaced along a cutting bridge, which bridge, in turn, can be displaced in guides along a cutting table, which accommodates the flat material. The laser cutting head can be placed above every point of the machining region of the flat material in two, preferably orthogonal directions, by means of this guide system. The laser cutting head can further preferably also be raised or lowered, respectively, vertically to the surface of the cutting table and thus also of the flat material.
The bridge, which supports the laser cutting head in a displaceable manner, is typically made of a box-shaped profile, which has an approximately rectangular cross section, which is guided far below its center of gravity, whereby a cable drag comprising supply, control and sensor lines, is also guided along the bridge to the laser cutting head. Examples for such substantially rectangular profiles for the bridges of laser portal machines can be found in DE202005014428, in WO201360392 or in WO2015086724.
Such bridges of rectangular box profiles of sheet steel have the disadvantage of the parallelogram effect, of an often relatively low stiffness-to-weight ratio, and of the unfavorable center of gravity position of the cutting carriage comprising the cutting head outside of the force transmission locations to the support structure. In the case of these designs, a bellows, which is provided if need be, is furthermore located directly in the region of the laser reflections and splashes of hot, molten materials, which start at the machining zone and which can badly damage the bellows, on the side of the cutting head.